This invention relates to an improved olefin oligomerization process and catalyst for preparing C.sub.6 -C.sub.30 olefin products. In another aspect, the invention relates to a method for preparing said catalyst.
Olefin oligomers are used for a variety of industrial products and have been produced by a variety of catalytic processes. For example, U.S. Pat. No. 3,424,815 describes the preparation of alpha-olefin oligomers using a catalyst comprising the product of certain nickel chelates with a halide-free organoaluminum compound such as alkyl aluminum alkoxides. Patentee teaches that the nickel chelating ligand-anion is substituted with electron withdrawing groups, i.e., nitro, halo, cyano or carboalkoxy and that superior results are obtained when the chelating ligands are halogenated organic ligands.
U.S. Pat. No. 3,592,870 discloses olefin dimerization catalysts formed from an organoaluminum compound and one of the following nickel complexes: (a) bis(beta-mercaptoethylamine)nickel (II) complex; (b) alpha-diketobis(beta-mercaptoethylimine)nickel (II) complex; (c) S,S-disubstituted bis(beta-mercaptoethylamine) nickel (II) complex; or (d) S,S-disubstituted-alpha-diketone bis(beta-mercaptoethylimine)nickel (II) complex. Under (c) and (d) are included complexes of the formulas: ##STR1## wherein X is halide and R.sub.1 and R.sub.2 are certain enumerated organic radicals and R.sub.3 is as defined for R.sub.2 or hydrogen.
U.S. Pat. No. 4,069,273 describes a process for dimerizing low molecular weight linear alpha-olefins using a complex of bis(1,5-cyclooctadiene)nickel and hexafluoro-2,4-pentanedione as the catalyst. Patentee describes his process as producing a highly linear olefin product. U.S. Pat. No. 4,366,087 describes a process for oligomerizing olefins using a catalyst containing a nickel compound having the formula (R.sub.1 COO)(R.sub.2 COO)Ni, wherein R.sub.1 is a hydrocarbyl radical having at least 5 carbon atoms and R.sub.2 is a haloalkyl radical and an organic aluminum halide. As can be seen from the examples in this patent, patentee's process afforded a product containing a large amount of branched olefins. A number of catalyst systems used for the polymerization of olefins are described in Chemical Review 86 (1986) pp. 353-399.
One of the principal uses of C.sub.6 -C.sub.30 olefins is as intermediates for detergents, e.g., sulfonated alkyl benzenes. When used for this purpose, the C.sub.6 -C.sub.30 olefin product should have a high proportion of linear olefins because detergents produced from linear olefins are generally more readily biodegraded than those produced with branched olefins. Similarly, mono-branched olefins are generally more readily biodegraded than multibranched olefins and accordingly, more desirable for detergents.